


I'll Be Right Here (To Hold You When The Sky Falls Down)

by Blackrising



Category: Overwatch (Video Game)
Genre: Alpha Zarya, Alpha/Beta/Omega Dynamics, Alpha/Omega, Dom/sub Undertones, F/F, Femslash, Futanari, G!P, Girl Penis, Knotting, Mating Cycles/In Heat, Omega Mercy, Omega Verse, Smut
Language: English
Status: Completed
Published: 2016-10-23
Updated: 2016-10-23
Packaged: 2018-08-24 05:26:03
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 10,297
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/8358988
Author URL: https://archiveofourown.org/users/Blackrising/pseuds/Blackrising
Summary: Zarya waited until Mercy held her gaze. “You are in heat and I am an Alpha. I am strong.” She grinned as she flexed her biceps for the shortest of moments, ridiculously enough to make a smile twitch at the edges of Mercy’s lips. “But you do not want me to mate you.”Mercy gritted her teeth and swallowed, searching beyond the haze of lust and pheromones in her brain for an answer.“What if I do?”The Alpha’s smile didn’t waver. “You rejected me before, Ангел.”- OR -Mercy miscalculates, Tracer plays matchmaker and Zarya really just wants to help.





	

**Author's Note:**

> Title comes from 'Right Here' by Ashes Remain, which is giving me all the Zarcy feels right now.

A drop of sweat clung to her brow. Mercy blinked, grimacing as the fluid dripped into her eye and momentarily blurred her vision.

“Dr. Ziegler?”

She shook her head and refocused on the task at hand. Her fingers slipped for the shortest of moments, accidentally putting too much pressure on the wounds on Genji’s face where his mask had cut into it painfully. His armour and limbs were usually stable, but a vicious punch had managed to make his face plate cave in.

She mumbled a quick apology when it happened again.

“Are you alright?” he asked, worry in his robotic voice, though it might be out of concern for his face more than for her. “You seem nervous.”

Mercy looked down at her hands. They were trembling, shaking, and underneath the thin skin of her wrist she could see her blood pumping faster. She drew in a slow breath to clear her head, grateful that Genji’s scent was muted and pleasant. For an Omega, he didn’t smell particularly comforting - too much of his natural scent was covered by plates of metal – but everything about him was blessedly neutral. He couldn’t smell her, either, which made it far easier to ignore the chemical processes in her body.

“I’m fine.” She didn’t try to smile, knowing it would come out stretched and strained. “We’re almost finished.”

Almost finished. She suppressed a shudder, heat trickling down her chest to settle in the pit of her belly. As soon as she had made sure Genji’s wounds wouldn’t get infected, she was free to leave the make-shift medical center she had claimed as her area of operations after it became clear they would need a central spot to take care of any injuries sustained during battle – she’d be free to lock herself in her room and get through this, as she always did. She’d have to make sure her teammates knew she wouldn’t be available for the next two days, but they’d be able to take care of themselves for however it long it took her to get her body back under control. None of them had her expertise, but even Junkrat could administer basic first-aid if it was needed, though she suspected he’d never actually used that particular skill before.

Genji hissed and Mercy shook herself. It wouldn’t do to let her mind drift while she was attending to a patient. She’d sworn an oath and she had worked years to gather the respect she needed to be taken seriously as a doctor, to be acknowledged as a skilled and cool-headed medic, Omega or not.

She could operate on anyone at any time, even when she was in the throes of heat.

“You are shakin-“

“I know!” Her snapped answer made Genji shut his mouth with a click, his eyes wide in surprise. She never snapped. She certainly never felt the urge to throw one of her patients out of the room just so she could be alone and take care of the incessant pounding at the back of her head.

Mercy had never been lax about her own body. Her medication regime was meticulously planned and enforced, one pill once a day from the 15th to the 20th of every month so her heat came and went with the smallest possible disruption to her daily routine. Every month on the 17th at 2pm, she retreated into her own private space and spent the time until she was fit to return to duty sating her body’s demands.

She was back at work by 2pm on the 19th, every month, every year without fail. This time should have been no different.

Swallowing hard, Mercy threw a glance at the digital calendar hanging on the far wall, already knowing what it said because she’d stared at it for a few long hard minutes before Genji had needed her attention.

It was the 14th.

Not the 17th as it should be, not even the 16th – it was the 14th of October and Mercy was in heat.

She hadn’t even taken any suppressants yet because her cycle had been as regular as possible since the day she’d turned fourteen and had almost broken a door handle trying to scramble into her room. Everything she knew about her own body told her she should have been good for another three days.

Genji didn’t make the mistake of opening his mouth again, but he observed her carefully as she finished cleaning and bandaging his wounds as quickly and efficiently as she could under the circumstances.

Mercy closed her eyes and took a deep breath, willing the quickening of her heart to settle. This didn’t feel like her usual heats. This didn’t feel like the gentle pulsing of energy behind her navel or the gentle coaxing of her brain to find an Alpha to mate with. The sweat on her back felt cool on her heated skin and the pounding in her head made it so very hard to think clearly, to catalogue the reactions of her body as she would have liked to do.

She wanted to think she had simply been so preoccupied that she had missed the first stages of her heat, that she was far further along than she’d anticipated, but she hadn’t felt so much as a twitch until an hour ago.

Her heat had just begun to build and that meant Mercy had to get out of there. As soon as possible.

“I’m sorry for snapping at you,” she said and gestured for Genji to hop off the examination table. She meant it, but the words came out too sharp anyway.

He nodded and bowed in thanks. “It is no problem. As always, I am grateful for your care.”

Mercy suppressed the urge to tap her foot impatiently while he gathered his mask and turned towards the door. He hesitated.

“I do not wish to impose, but,” Genji scanned the nervous jerk of her shoulders and her crossed arms. “Perhaps it would be better to let someone help you.”

Mercy stopped breathing at the suggestion. “Genji, you know very well I can’t do that.”

She had spent most of her life avoiding entanglements, for her job and for herself, and to think he would suggest she go off and let someone breed her-

His brow knitted in confusion. “You are a very capable doctor, of course, but it can’t be helped if you are sick.”

Of course. Genji had lost most of his sense of smell years ago and due to his cybernetic limbs, his natural Omega biology had all but ceased – he hadn’t experienced the desperation of heat in a long time and he had no reason to suspect her cycle would suddenly change.

“I’m not-“ She sighed. “I will. Thank you.”

He seemed happy enough that she was willing to heed his words and finally turned to leave, the door clicking shut behind him. Mercy waited, one beat, two, until she was sure Genji was gone, before she leaned heavily against her desk and took a few deep breaths.

In and out, in and out.

It was a tactic that just barely worked and only when there were no disruptive scents to throw her off course, but it helped clear her head for a moment. With trembling fingers, she brushed a strand of sweat-matted hair back from her forehead, haphazardly putting her desk in order and trying to shrug out of her lab coat at the same time.

She didn’t trust herself to stroll around, not in the state she was in. She’d have to write a note, or give Winston a call if she could form the necessary words, or maybe-

The sound of the door hissing open made her stiffen mid-movement.

“Howdy, Doc.” McCree strolled in with a tip of his ratty hat before throwing it on a nearby table. “We’re back and got some scrapes for you to take care of, if you don’t mind.”

Mercy held her breath. Jesse was a Beta, his scent bland and his very demeanor polite and uninteresting for an Omega in heat. If it was just him, he would pose no threat.

“Jack’s taking care of himself as usual, but Tracer got banged up pretty badly. Haven’t seen her during the mission, but she was limping when she came back.”

He kept blathering on while he got rid of his shirt and Mercy clenched her jaw. The scent of Alpha around him was dim, mere traces of the people he’d interacted with, but it tickled her nose and made saliva gather in her mouth. It wasn’t Jack’s smell that covered him, but something stronger, more visceral. Virile.

The heated energy in the pit of her stomach spread, the desire to be bred slithering into every limb. This wasn’t supposed to happen - not here and not yet.

“Zaryanova took a hit for me out in the field. Covered me from the blast. She seemed alright, but it’s hard to tell with her.”

Mercy squeezed her eyes shut. So that’s what it was.

Zarya was a special brand of Alpha. Large, broad-shouldered and confident, prideful in her strength and dominance oozing from her every pore. Much like Reinhardt in his prime, she was everything an Alpha was supposed to be.

Mercy had always thought herself largely immune to traditional Alpha charms – Reinhardt, Jack, all the Alphas she had met over the course of 37 years, none of them had drawn more than a second glance from her, especially once she’d started taking her suppressants.

Aleksandra Zaryanova had done a splendid job of destroying that notion when she had walked into her first pre-mission meeting with her arms bare and glistening from a previous work-out, muscles pumping underneath her skin and the scent of her sweat enough to bring even the most controlled of Omegas to their knees. Mercy had gone into that mission near unprepared after she had spent most of the meeting cowering in a corner and covering her nose.

Back then, she’d chalked it up to the fact that she hadn’t anticipated another Alpha to join them. She’d been surprised and easily overwhelmed, her body not used to being in a room with so many Alphas at once.

She certainly hadn’t expected herself to grow so…attached to the other woman and even now, she couldn’t quite explain _how_ it had happened. There had been late night conversations when she couldn’t sleep, growing worry at every new injury and laughter when her shoulders felt almost too heavy to bear.

There had been a kiss.

Mercy remembered it – it had been late, dark, and she had only meant to wish her goodnight. Stretching up to kiss the Alpha had been an accident, a testament to the exhaustion settling in her bones after a hard day and making her forget the distinction between friend and lover, but her lack of protest when Zarya had taken her into her arms and pressed her into the cushions of the couch had been deliberate.

Deliberate and stupid and she’d allowed herself to enjoy it anyway, the weight of her , how the heat of her arms and body could encase her entirely and the warm roughness of her mouth.

She’d writhed against Zarya, wrapped her legs around her waist and tugged at the short hair at the back of her head like she didn’t know it was a mistake, like she was a stupid teenager again with no more on her mind than the hardness pressing into her stomach, like her libido wasn’t supposed to lie still and dead when she wasn’t in heat.

It had taken Hana walking in on them with a sandwich threatening to slide from between her lips and a bottle of soda held between her fingers to pull Mercy out of her trance and make her flee.

Ever since then, she’d made a point of avoiding the Alpha. She couldn’t afford a relationship, she couldn’t afford that kind of attachment, she couldn’t afford to care any more than she already did.

With a hard swallow, Mercy threw another glance at the calendar on the wall, the digits glaring at her defiantly. The 14th.

“Uh, Doc?”

As much as she’d tried to avoid her, Zarya’s scent lingered. She’d ignored the flickers of arousal in her belly when she caught a whiff of pheromones clinging to the weights in the fitness room or to a chair,  the shiver climbing up her spine when she brushed by her in the hallway and even the tremor in her own limbs when Zarya carefully pushed her to safety in battle. She’d ignored all of it without considering long-term effects.

Like her body reacting to the onslaught of pheromones by breaking its soothing cycle and going into heat far sooner than planned. She’d studied Omega biology extensively, she’d read all about how unusual stimulus could trigger heats, had talked to a number of Omega patients who had gotten pregnant as a result of putting too much trust in the steadiness of their heat cycles – she should have known to be careful.

“Doc!”

Mercy’s head snapped up. McCree had uncovered a nasty wound on his shoulder and was regarding her with a frown. “You okay there?”

She loosened her white-knuckled grip on the edge of the desk and straightened, attempting to calm her increasingly heavy breathing.

“I-“

Before she could fabricate another lie about her state or explain away the sweat gathering in the hollow of her throat or the constant shifting of her thighs, the door to her office opened again. Mercy very much felt like burying her head in he hands.

“Oi, Doc, you got some time?”

Mercy didn’t have to look up to recognize Lena’s voice and groaned silently to herself. She had to get out of here and to her room, somewhere she could be alone and get herself off to thoughts of Zarya’s large body covering hers, to thoughts of her rough voice growling into her ear. She could barely deal with one patient, much less two.

As soon as she’d crossed the threshold, Lena’s mouth shut with a click and she raised her nose to sniff at the air. Her eyes narrowed in contemplation. “Anyone else smell that?”

Mercy curled her hands into fists and stumbled back. As an Omega herself, Lena would have no trouble recognizing the concentration of pheromones in the air.

McCree shrugged. “I can’t smell a thing. What about you, Doc?”

She hissed and pressed herself against the wall. The room was too small, too hot, and they all had fragments of Alpha scent clinging to them like a cloak. How Lena could seem to be entirely oblivious to it was a mystery, but the wide eyes coming to rest on Mercy were clear.

“Oh bollocks,” she mumbled. “It’s early, isn’t it?”

Mercy forced her shoulders to relax and nodded. “Yes, but don’t concern yourself with me.” She smiled stiffly and carefully hid her trembling hands behind her back. “You needed something?”

“It’s not an emergency. And I reckon you got something else on your mind anyway.” Lena’s surprise had rapidly transformed into amusement and she grinned widely, a mischievous twinkle in her eye.

Jesse, for his part,  just seemed confused.

“If you are hurt, you require treatment,” Mercy reminded the young woman sternly, even as her body urged her to take the offer.

“Don’t worry yourself, Doc, I’ve got it all under control.”

The meaning in her words was layered and Mercy had known her long enough to be wary of that particular tone, but she couldn’t find a reason to stop her as she turned on her heel and hurried out of the room with a last ‘everything’s gonna be just fine!’ thrown over her shoulder.

After a moment, Jesse cleared his throat. “Did I, uh, miss something here?”

Mercy sighed with a shake of her head and silently gathered the last reserves of her willpower as she offered him a seat. To his credit, he didn’t needle further.

She’d always been the type to work quietly unless something needed to be said and she almost managed to put the desire burning in her gut out of her mind as she carefully worked the bullet out of his shoulder.

If her unsteady hands hurt him more than absolutely necessary, he didn’t mention it.

Working with Overwatch had taught her a lot of things and removing a bullet, cleaning and bandaging the resulting wounds – it was something she could do in her sleep. Even when all her concentration was needed to stop her teeth from chattering and her shoulders from convulsing with shivers.

Just a few more minutes, she reminded herself. Once Jesse had left, her thoughts were free to wander where they may. It wouldn’t be as satisfying as the real thing, as having Zarya in her, but it was uncomplicated. Safe.

“All done,” she announced, eventually, _finally_ , and felt like the smile was frozen on her face. “Keep the bandage dry and it will all heal quite nicely.”

“Thanks. Mighty fine of you, Doc.”

He gathered his shirt and hat and hesitated, as if wanting to speak again. Mercy was immensely grateful when he seemed to decide against it and simply tipped his hat before striding out of her office.

When the door finally closed – for the last time today, she prayed – Mercy crumbled against the table. The floodgates in her mind opened to allow her thoughts to spring forth, heated and filled with the scent she was craving, and her fists balled atop the table until her nails left painful indents in her palm.

Sweat dripped down her back.

Having realized it was Zarya’s presence in her life that had turned her hormonal balance upside down, it was nigh impossible to stop herself from spinning it further. What would have happened if she hadn’t run away? What would have happened if Hana hadn’t walked in on them, if the interruption hadn’t caused Zarya’s hand to jerk away from the waistband of her pants?

She wouldn’t have stopped her.

The Alpha would have slid her fingers between her legs and found that she was wet, ready and wanting, and Mercy would have pressed against her in a silent plead for _more_.

Zarya would have fucked her right there on the couch, even though Mercy was an Omega, even though it would have caused an untold amount of problems, even though Mercy hadn’t even been close to her next heat.

The sterile white walls of her office faded as she gave herself over to the fantasy.

The Alpha had already been rock-hard as she’d lain on top of her, skin flushed and voice low and gravely, and as Mercy imagined sliding her finger down to cup her erection, her real hand inched beneath her own waistband.

She should wait until she was in her room, she knew that, but her finger glided through her wetness almost of their own accord and she shivered pitifully. It was ridiculously easy to imagine Zarya’s scent surrounding her. Her own hand would never be enough to satisfy the gnawing hunger in her veins, but it might be able to take off the edge until she felt capable of walking to her room.

She brushed the pad of a finger over her clit, biting her lip to stop the noise building in the back of her throat, and imagined it was Zarya’s much larger hand between her thighs, imagined breathing in her heady, musky scent as the Alpha murmured encouraging words into her ear.

If she hadn’t been so distracted by her own desire and the pictures in her head, she might have heard the door opening. She might have heard the shuffling of heavy feet. She might have heard the sharp intake of breath or the snap of teeth.

Someone cleared their throat.

Mercy’s finger’s turned to stone, her spine snapping straight and her eyes widening. She didn’t want to turn around. She didn’t want to look towards the door and get confirmation of what she was already beginning to understand – that the heady scent clogging up her throat was not just a figment of her imagination.

“Lena has said you wished to speak to me?”

Zarya. Mercy’s nostrils fluttered – she would recognize the heavy brand of her scent anywhere, would be able to pick her out of a crowd without so much as a second thought.

In the back of her mind, she was aware that she hadn’t removed her hand from between her legs even as she turned to face the Alpha. Tall and broad, Zarya took up nearly the entire doorway where she casually leaned against it, her muscular arms crossed in front of her chest.

Her expression was unreadable.

Mercy opened her mouth to respond, to explain or to plead, she couldn’t be sure, but the only word her lips could form was a name.

“Zarya…”

Unbidden, the finger on her clit started moving again. Slow, harsh circles that made her hips buck and her gaze zero in on the other woman’s tall form, like just staring at her might sate her need. Like the plea in her eyes would be enough to make Zarya spring into action and give her what her body so badly craved.

“Stop.”

Mercy’s motions halted immediately, her thighs trembling. Zarya’s tone left no room for argument and the pheromones in the air made sure she had no choice but to obey the command, even as the throbbing between her legs begged her to continue. Even as it took all her willpower not to throw herself at the other woman like all the years she had spent avoiding this exact predicament had been for nothing.

Zarya moved towards her and Mercy held back a whimper in anticipation of her first touch. Angling up her face to offer her lips for a kiss, she closed her eyes and waited with bated breath.

She waited, but the slide of soft lips against hers never came. Instead there was one strong arm behind the hollow of her knee, one at her back, and she suddenly found her world turning.

“Do not worry, Doctor. You are safe.”

Mercy’s eyes blinked open when she was scooped up and her heart threatened to bruise her ribcage when she caught sight of pink hair, a broad grin and sparkling eyes so near. Eyes that flashed dark and dangerous, just for a moment, before returning to their usual soft green. The scent of Alpha was overwhelming in her embrace, the heat of Zarya’s skin searing into Mercy’s body and she groaned, burying her face in the crook of the other woman’s neck to breathe in deeply.

Her blood, the part of her that reveled in being help captive against a broad chest, sang as the Alpha jerked for the shortest of moments.

“You will be in your room very soon,” Zarya murmured, her breath hot and heavy against the crown of Mercy’s head. “Stay strong for a little longer.”

Mercy didn’t want that. She didn’t want to be taken to her room and she didn’t want to be alone – she wanted what the husky quality in Zarya’s voice promised, what she’d been so close to taking that night on the couch.

Her fingers clawed tightly into the folds of Zarya’s track jacket.

“Why?” she choked out, and she couldn’t tell what she was asking. Why was Zarya here? Why was she still willing to help her? Why wasn’t she pressing her against the wall and taking her the way Mercy wanted her to?

Zarya sighed and tucked her firmer against her body, pressing a frustratingly innocent kiss to the top of her head. “Lena has said you had gone into heat. And that she was worried an Alpha would take advantage of your state.”

The memory caused her arms around her to tighten and an inaudible growl to rumble through Zarya’s chest. The reaction soothed an instinctive part of Mercy and she managed to turn her face from the warm patch of skin she’d been resting against to release a breathless chuckle.

Lena did not have a single manipulative bone in her body, but she knew as well as any Omega how to push an Alpha’s buttons. Their protective instincts were an easy target.

“I will protect you,” Zarya assured her and Mercy couldn’t tell whether the hint of possessiveness in her voice was a product of her own need or not, but the pounding in her limbs made it so very hard to care. Her thoughts were already paling, fading in favour of her body’s demands. Against her fingertips, the strong muscle beneath Zarya’s chest pumped and, absentmindedly, Mercy pressed her lips to the underside of her jaw. The Alpha tensed.

“We should go.”

Mercy ignored the husky words and nibbled on the skin beneath her lips instead. Her instincts, momentarily content now that she was in the arms of someone who could satisfy her, who could knot and breed her, urged her to purr and get as close as she possibly could.

“It will be easier then.” Zarya’s throat vibrated with every word.

Mercy shook her head, whining at the implication. “No,” she murmured and pressed her face into Zarya’s chest. “Please. No.”

The Alpha was quiet for long moments and Mercy could _smell_ it – the kick of Alpha arousal saturating the air around them, the pheromones that told her Zarya _wanted_ to fuck her, to knot her. Just like she had wanted to when Mercy had kissed her.

Despite this, Zarya’s tone was light-hearted as she spoke. “Your instincts are strong.” She moved towards the door. “But you will think differently in a few days.”

“No!”

Mercy surprised herself with the strength with which she pushed away from Zarya – not enough to truly overwhelm her, never that, but enough to surprise the other woman into letting her slide to the ground.

She didn’t attempt to stand on her feet, instead using her momentum to fall to her knees in front of the Alpha. The smile on Zarya’s face fell away as Mercy met her eyes from beneath lowered lashes, pressing her thighs together to soothe the pulse of arousal between her legs at her new position.

Under normal circumstances it would be humiliating to behave like this, but Zarya’s unintentionally pleased growl made Mercy forget whatever shame she might have been feeling as she whimpered and pressed her lips against the Alpha’s clothed crotch.

She was hard. Rock-hard underneath the soft fabric of her pants and Mercy let out a relieved breath as she nosed along the seam, rubbing her cheek against the swelling erection she needed so badly. Zarya jumped in surprise, but didn’t push her away.

Mercy wanted to hook her fingers into her waistband and pull, to watch her length spring free and take it into her mouth – she wanted her knot in her and she didn’t care how -  but her arms hung useless at her sides as she could do nothing but breathe in the scent of her lust and pepper kisses wherever she could reach.

“Please,” she repeated quietly, panting.

“Ангел…”

Whatever Zarya might have said was cut off as Mercy parted her lips and ran her tongue along the bulge of her cock. All she tasted was cotton, but from the corners of her eyes she saw the Alpha’s hands curl and uncurl reflexively. Her mouth opened to do it again, to display her need the only way she knew how at that exact moment, but suddenly there was a tight grip on her jaw and her face was pulled away gently.

Zarya crouched down in front of her and Mercy gave an unsatisfied whine.

“Ангел- Mercy.” The hand upon her jaw loosened its hold and a thumb traced along her burning cheek and the side of her mouth, never straying towards her lips. “Look at me.”

The way Zarya pronounced her call sign had always been a bit strange, rolling roughly along her tongue like she wasn’t quite sure what to do with it, but Mercy found it oddly charming. More importantly, it made her listen.

 Zarya waited until Mercy held her gaze. “You are in heat and I am an Alpha. I am strong.” She grinned as she flexed her biceps for the shortest of moments, ridiculously enough to make a smile twitch at the edges of Mercy’s lips. “But you do not want me to mate you.”

Mercy gritted her teeth and swallowed, searching beyond the haze of lust and pheromones in her brain for an answer. “What if I do?”

The Alpha’s smile didn’t waver. “You rejected me before, Ангел.”

“I-“

_-didn’t._

But she had. If she hadn’t gone into heat, if Lena hadn’t tried to play matchmaker, Mercy wouldn’t be here right now. She’d still be avoiding Zarya out of fear of- of what? Her head was pounding, the heat in her gut aching, and she couldn’t remember why she’d been afraid, only that the realization that it would be easy – too easy – to fall in love with this woman had made her want to retreat and bury her emotions the way she had always done.

Zarya’s eyes softened, her legs tensing as she prepared to stand up, and Mercy found herself shaking her head frantically.

“Wait.” She resisted the urge to turn her head and take the thumb that was resting at the corner of her mouth between her lips. Her heat was held at bay by nothing more than her desire to express what she hadn’t been able to say since they had kissed and she could already feel the lust encroaching on her senses to envelope her once more.

“I was afraid,” she said, clenching her jaw to stop her teeth from chattering. “I can’t- I would have cared too much.”

She didn’t know if her words made sense to anyone but herself. A doctor was supposed to care, to have empathy for their patients, but to get attached meant getting hurt. To trust someone to take care of her meant an emotional vulnerability she hadn’t been able to afford in a long time, not since the day she had lost her first patient to a simple fever.

“But I need you.”

That, at least, was as straight-forward and honest as she could possibly be. Here, right now, she needed Zarya to knot her – desperately. Her fears and doubts had no room in her heat-addled mind.

 For once, she had an excuse to be _selfish_.

“You do not need _me_.” Zarya shook her head, her tone conveying nothing but friendly indulgence. “Your body just wants a knot.”

Mercy wanted to groan at Zarya’s stubborn refusal. She was an Alpha, she’d kissed her, and Mercy didn’t need to draw on her medical expertise to recognize the wide pupils and tense muscles for what they were. She wanted to tell her that she had changed her mind, that she was ready to commit in whatever way they both desired, that she was no longer afraid of what could happen if she gave in, but it would be a transparent lie.

She was still terrified. She still couldn’t promise that she wouldn’t run again from the possibilities, the _chance_ , Zarya represented    .

Instead, she grasped the sides of the other woman’s face between her hands and kissed her. Clumsy, harsh, desperate to drink in her scent and her presence, her strength.

Desperate to feel that sense of peace she’d thought she’d lost so long ago.

“Then give me that,” she panted as she drew back an inch, her breath brushing against the Alpha’s unresponsive lips. “Please. At least give me that.”

Zarya’s mouth opened in a surprised intake of breath as Mercy splayed trembling fingers across the hard expanse of her stomach before sliding down and shoving them past her waistband to take a firm hold of the Alpha’s pulsing erection. It was hot and hard in her palm, big enough to make the Omega in her purr in anticipation, and Mercy took the opportunity to delve into the other woman’s mouth with her tongue, silently begging for her to return the kiss.

“Knot me,” Mercy whimpered into her mouth, squeezing the cock in her hand for emphasis. The throbbing between her legs was too strong, to insistent and tempting, and instinctually, she wanted nothing more than to turn around, lower her torso to the cold floor and present herself to Zarya as wet and aroused as she was.

She wanted nothing more than for Zarya to mount her. To press her into the ground and use her until her knot was lodged within her, deep and uncompromising and-

The Alpha growled deep in her chest.

Without quite realizing it, Mercy had started jerking her off in rushed bursts, moving along the soft skin as much as she could in the cramped confines of the other woman’s pants. When she forced her hand deeper to cup the Alpha’s balls, something in Zarya’s posture changed.

Her hips twitched, once, before she groaned and pulled her lips away from Mercy’s. “I am sorry, Ангел.”

All at once, Mercy’s hand was wrenched away and she found herself lifted up again, thick arms tightly wrapped around her waist. But Zarya didn’t make for the door as she might have feared – her rapid steps brought them to her desk and with a quick swipe of her arm, she had freed the space to deposit Mercy upon it.

Not for a moment did Mercy consider the damage to her equipment, because Zarya had braced both arms at her sides and was nosing along the tendon in her neck, the rumble in her throat low and husky and pleased.

“Last chance,” she warned her, raising her head to look down into Mercy’s half-lidded eyes with a seriousness she rarely displayed outside of battle. “I will not stop.”

Mercy licked her lips, a small voice in the back of her mind wondering if she really wanted to cross this line. If she could live with the consequences.

“Then don’t.” Her body had made that decision a long time ago. She laid her hands on Zarya’s broad shoulders and raised her legs to wrap them around her hips, urging her to press flush against her. “Don’t stop.”

Zarya waited a beat, as if Mercy might change her mind.

Then she smiled.

It was a familiar smile, broad and just a tad mischievous and Mercy couldn't deny that the kind humour in it soothed her anxiously thrumming heart somewhat.

"I've never been knotted before," she said, quietly but clearly.

"Do you want me to go slow?"

Mercy swallowed and tightened the hold of her thighs around the other woman until the hardness of the Alpha's cock was pushed tightly against her crotch. "…no."

The concentration of Alpha pheromones in the air kicked up a notch and Zarya raised one hand to quickly work the rubber band out of Mercy's hair before pressing a kiss to her temple.

"I will take care of you," the Alpha growled, breathing in deeply, and there was no doubt in Mercy's mind that she could trust her to do just that.

Mercy's head fell back as Zarya ran the flat of her tongue up the arch of her throat, closing her lips around her pulse point to softly suck at the skin – _marking_ her.

A gentle bite caused Mercy to push closer to the teeth at her neck and roll her hips against the other woman's in a useless attempt to soothe the pulsing between her legs. The Alpha chuckled and moved her hips away.

"Please, Zarya-"

"My name." She bit at the skin of her throat again. "Say my name."

Mercy gripped the soft hair at the back of Zarya’s head between her fingers and urged her to bite harder, to leave a reminder for everyone to see.

“Aleksandra,” she hissed, the wetness between her legs dripping down her thighs with every nibble of even teeth.

The Alpha nodded, approving, and straightened. “Your clothes. Off.”

Without an ounce of hesitation, Mercy struggled out of her lab coat, uncaring of how ridiculous the contortions of her body might look. Her sweater was a bigger issue and she couldn’t seem to tug it over her head, no matter how desperately she tried.

She felt utterly useless – near delirious with arousal and failing at a simple task like undressing herself. She felt like a child.

Zarya made a calming noise in the back of her throat and slid both of her hands underneath the fabric covering her torso, pulling it upwards as she went. They were large and warm, her palms alone able to cover her from rib to rib, and Mercy momentarily forgot her predicament as she arched into the touch.

They brushed against her bra for a moment, over her straining nipples, before pulling the garment off with a gentle tug.

Mercy missed the weight of her hands immediately.

“You are very beautiful,” the Alpha murmured, running a single finger down her breast bone to the edge of her bra.

If she’d been capable of doing anything but avert her eyes and suck in quick breaths, Mercy might have argued the point. She was sweaty, red-faced and her underwear had been chosen for comfort rather than seduction – everything about her was messy and she couldn’t see how that might be appealing.

Zarya’s stare made the heat in her belly spike even as she wished she wouldn’t look at her disheveled appearance quite so closely, dark green eyes roaming over her skin like a physical caress. Hoping it would propel the Alpha into action, Mercy reached down for the hem of her skirt with shaking fingers and pulled it up to her hips.

The sight of her thighs drew the other woman’s gaze like a flame and her hips twitched at the hunger radiating from the tense set of Zarya’s muscles.

“Closer,” she panted when the fabric was finally bunched up around her waist and her drenched panties lay bare. They felt restrictive, wet and clinging like a second skin. “Aleksandra- I need you closer.”

Zarya bared her teeth – grin wilder and hungrier than Mercy had ever seen, and holding a promise that sent a shock of arousal straight to her groin. Hooking a finger underneath the rubber waistband of Mercy’s underwear, the Alpha tugged it down her legs and off, throwing the garment over her shoulder with a careless shrug.

It was a relief to be rid of it.

Mercy shivered at the cool air brushing over the burning hot flesh between her thighs – her legs were spread, the arousal and need leaving her open and glistening. Twitching with every beat of her heart.

When Zarya’s hands curled around the outside of her thighs, she squeezed her eyes shut and opened her legs as far as they would go. Inviting. Pleading. Begging the other woman to fuck her.

The rustling of clothes and the noise of a zipper made Mercy bite her lip and hold her breath in anticipation, a part of her aching to look down and see Zarya work her cock out of her pants, but a bigger, more insistent part urging her to keep still and submissive while the Alpha prepared to breed her.

Zarya clicked her tongue admonishingly. “Look.”

It took more willpower than it should, but Mercy blinked and met the other woman’s intense stare. She attempted to hold it, but her eyes instinctively darted down to the Alpha’s groin, her mouth opening in a silent moan at the sight of Zarya’s hand wrapped tightly around her cock.

She should have been worried about the size of it, about the size of the knot that had yet to pop, but her clit twinged and some long-forgotten muscle inside of her clenched around the painful emptiness within her.

“You have said you need me. But do you _want_ this?” Zarya squeezed and Mercy’s hips jumped in sympathy. When she didn’t immediately respond, the Alpha laid her palm on top of her thigh, her thumb hovering teasingly above her drenched slit. “Answer my question, Ангел.”

Her tone was still light-hearted, still kind, but there was a steely kind of quality underneath it that made it clear she expected her orders to be followed. Mercy arched her hips off the desk, hoping for that illusive contact, but Zarya merely shook her head and moved her thumb back.

“I will take care of you,” she repeated, her expression softening from bright and humorous to something more meaningful. “All you have to do is answer.”

Mercy groaned. “Yes.” She writhed, eyes fixated on the swollen head of the Alpha’s cock and the pearly drop of fluid resting in its slit. “Yes, I want this.”

Almost immediately, Zarya slid the pad of her thumb gently between her folds and up to her clit. Mercy’s legs shook with tremors as she began to circle it in a steady rhythm and her head threatened to fall back at the sudden onslaught of pleasure racing down her spine, only to be stopped by a hand closing around her jaw.

Zarya’s erection, no longer restrained by her fingers, twitched against the fabric of her top. Mercy turned her head and sucked the finger resting against her cheek into her mouth, chasing the remnants of the other woman’s taste and groaning around the digit when she saw the Alpha’s cock give a harsh throb in response out of the corners of her eyes.

“Tell me _what_ you want,” Zarya coaxed her with a pleased hum in the back of her throat, keeping the brush of her thumb around Mercy’s clit even and uninterrupted. Even had she known what to say, Mercy wouldn’t have been able to answer.

Zarya was so near, the heavy scent of pheromones around them cloying and turning every breath into a stab of pleasure, the hand between her legs strong and steady and merciless in its motions, and her inner muscles tensed as she could feel her orgasm approaching.

She clenched in anticipation, sensing the first gentle waves building, and opened her mouth to moan-

Just as Zarya robbed her of the contact of her hand.

Her climax was stopped in its tracks, the accumulated pleasure seeming to settle in her gut as pure frustration and she whined softly, desperately searching for the Alpha’s gaze. Why?

“Not yet.” Zarya dragged her fingers wetly over Mercy’s soft stomach, but made no attempt to finish what she had started.

“But-“

“When you come, it will be with my knot in you.”

And just like that, the blocked arousal flared to life with a vengeance and Mercy strained to lift her hips in search of gratification that the sliver of distance between them couldn’t give her. As if she didn’t notice the action, the Alpha stretched and pulled her jacket off her shoulders and her tank top over her head – slowly arching her back as she did so.

Mercy’s eyes were transfixed on the hard planes of flesh it revealed, on the clearly delineated muscles of the other woman’s stomach that flexed beneath her skin with every movement. Most Overwatch agents were fit and trained in one way or another, many of them sporting a much better definition than Mercy could ever dream to have with her wide hips and softly rounded stomach, with her body that was built to showcase fertility rather than strength, but none of them moved her the way Zarya did.

None of them made her want to explore the outline of muscles beneath their skin with her tongue, to bask in the force the other woman commanded so easily.

Noticing her stare, Zarya winked and purposely tensed for a second before throwing the garment in her hands away with a flourish.

Without conscious thought, Mercy’s hand had started inching between her own legs. The Alpha’s cock was brushing against bare skin now and she could see the glistening traces of pre-cum it left. Her mouth watered.

Zarya bent over her again and tapped against her traitorous palm with a shake of her head. “Put your arms over your head.”

Mercy’s fingers stilled, but didn’t move away. It was so tempting to give herself a quick orgasm now, to rub herself to completion with Zarya watching, just to take the edge off.

“Your arms, Ангел.”

She whimpered and did as she was told, hooking her fingers around the table edge to prevent herself from masturbating after all.

The Alpha let out a harsh breath and nosed along the side of her face, lips grazing along the shell of her ear before she bit down softly.

“Good girl,” she whispered, and it took every ounce of willpower Mercy had not to grab her cock and push it into herself. “Keep your legs open.”

The muscles in her body quivered as Zarya took a hold of her cock and guided it closer. The first touch of the soft head against her folds caused Mercy to bite her lip hard enough to draw blood and she angled her hips upwards subtly to make it easier, to allow the Alpha to slip inside her in a single thrust if she so desired.

She didn’t.

Instead of the penetration Mercy expected, _needed_ , Zarya slid her rock-hard length through her folds until they were slotted together, until every pump of her hips would rub the underside of her cock across Mercy’s clit.

It wouldn’t satisfy her, not until Zarya fucked her and filled her with her cum, but Mercy eagerly met her first thrust anyway. She was wet enough to drip on the table underneath her and the Alpha met absolutely no resistance as she growled and smoothly grinded between her legs, every push firing off sparks of electricity in Mercy’s lower stomach and she knew, she just knew, that Zarya was testing her, teasing her to see if she could hold on any longer.

_When you come, it will be with my knot in you._

The sound of skin slapping against skin filled the room as the Alpha continued to rut against her, their fluids mixing on every pass. Drops of pre-cum were pooling in the dip of Mercy’s stomach as rivulets began to run down the taut skin of Zarya’s cock and leaked onto her at the apex of every thrust, proving beyond a doubt that the other woman was as ready to mate her as Mercy had been since the moment she’d walked into the room.

Her climax was building again. Just like before, the steady stimulation, the constant pressure on her clit made the ball of heat at the bottom of her spine threaten to unfurl and send her over the edge, just like before, her back arched in preparation as she could taste the first flickers of orgasm.

And just like before, Zarya stopped.

Tears gathered in the corners of Mercy’s eyes at being stopped _again_ , at feeling the release she’d been waiting for since she first went into heat dancing out of her reach and getting lost in the burning of her limbs, in the chaos of lust and frustration turning her usually rational mind into a puddle of mush.

She couldn’t help herself – she sobbed.

Loud and desperate, her body taut like a bow as she held herself stock-still despite the urge to pull Zarya into her.

_I will take care of you._

She believed her. She was wet and aching, hurting in ways that were both painful and undeniably exciting, but she believed her.

A gentle thumb wiped the tears from her cheeks and Zarya grinned as she placed a pleased kiss underneath her ear. “You are ready.”

Her arms wrapped tightly around her torso and Mercy clung to her, like she was her life line, her fingers and nails digging into the strong expanse of her back and shoulders. Zarya hummed soothingly and reached between them, placing the swollen head of her cock right at Mercy’s entrance and dragging it across her drenched skin in a tight circle for the shortest of moments.

Mercy was shaking. The flesh between her legs twitched periodically in unfulfilled arousal and excitement and she knew the Alpha could feel her clenching in an attempt to pull her in.

The first push made the breath catch in her throat. The bare tip alone stretched her deliciously and Zarya barely paused before sliding deeper, slow but continuously – it was torture. Just a bit uncomfortable due to her thickness, but so languid and mindful that Mercy could feel every ridge and vein as it scraped along her inner walls, as the head pressed into the spot that made stars burst behind her eyelids.

“Breathe, Ангел,” Zarya purred and nibbled lightly on her lower lip, licking at the blood Mercy had drawn.

Only when the Alpha was fully seated within her, when Mercy realized that every inch of her was filled with warm, throbbing flesh, that the very tip of her length rested snuggly at the entrance to her cervix, did she suck in a chocked breath.

The first roll of Zarya’s hips threatened to steal it right away again, but she forced herself to pull enough air into her lungs to stave off the dizziness even as the Alpha pulled back lazily – only to slam into her with enough force to make the desk underneath her rock and creak.

Mercy cried out sharply.

There was pain mixed in with the pleasure, but Mercy craved it, craved feeling the thick cock fill and stretch her almost beyond her limit, craved the ache of being pushed down and used. Zarya growled into her ear as Mercy’s inner walls tightened around her, but didn’t let it stop her from repeating the motion. Backing out slowly, giving Mercy’s body just enough of a reprieve to let her come down from the last push, before thrusting back in with as much strength as she could muster, over and over again.

“Fuck-“ Mercy didn’t curse often, didn’t like the crudeness of it, but the word tumbled out of her mouth instinctively and she could think of no other word to express herself. Her vision turned vague and blurry as the Alpha increased her speed slightly, pumping into her more frequently, even _harder_ if that was at all possible, the rumble in her chest turning into a near continuous drone. Every jerk of her hips caused the accumulated wetness between Mercy’s legs to drip down her thighs and onto the desk, the squelching sound of their mating embarrassing if she weren’t too far gone to care.

Her nails dug harder into the skin of Zarya’s back and she was barely aware of what she was chanting underneath her breath – a jumble of English and German, of ‘fuck me-’ and ‘Oh Gott, bitte-‘ and words she couldn’t remember as soon as they’d left her mouth.

The Alpha clutched her tighter to her chest. Her weight and presence was suffocating as she pressed her into the hard surface of the desk, but what might have been uncomfortable or threatening with anyone else felt like protection in the circle of Zarya’s arms.

And for the first time, there was nothing else than _this._ Mercy didn’t have to be the one to keep everyone else safe and protected, she didn’t have to be the caretaker, didn’t have to be the one held accountable.

 _I will take care of you_.

All she had to do was give herself over and let go of the demons that haunted her. All she had to do was trust the other woman to be there and catch her when she fell. Right now she wasn’t a doctor, an agent or a confidant. She was Zarya’s.

“You are doing so well,” the Alpha praised her with a grunt as she rutted into her, raising herself up on one arm to be able to look into her face. “Just a little longer. You can do it.”

Mercy gave a jerky nod and raised her chin, seeking out the other woman’s lips in a silent plea. Zarya obliged her with a breathless chuckle.

The way she kissed her held none of the gentleness of her tone and expression – it was possessive, brutal, as powerful as the way in which she pounded into her, and Mercy gave a helpless moan as she tried to give as good as she got, sloppily sucking the Alpha’s tongue into her mouth.

She only broke away when Zarya angled her hips and changed the rhythm of her strokes to something short and quick and aimed to put pressure on her sensitive front wall on every uncompromising pass. Every time she bottomed out, the hard planes of her stomach grinded tightly against Mercy’s clit and the blood rushing through Mercy’s ears drowned out everything except the encouraging words murmured into her ear.

Her body had reached its breaking point. The pleasure zinging through her was stacking, focusing into an explosion that she was afraid might render her unconscious, she was _so close_ – yet still she was hovering on the brink, rising ever higher as she desperately arched up in search of the final push.

She was leaving deep, bloody scratches in Zarya’s back, but the Alpha didn’t seem to be bothered by it.

Mercy almost didn’t notice the swollen flesh grinding against her entrance, not until it became too big to ignore. Zarya’s knot had started forming and it was _big_. She had expected it, in a way, ever since she’d first seen her, ever since she’d first caught herself idly wondering about her in the few private moments she could afford.

It pressed against her, insistently, and even despite already feeling like she’d never be able to take it, Mercy knew that it had yet to reach full size.

And despite her worry, she _wanted_ it.

“Aleksandra-“

“Shh,” Zarya intoned, one of her hands grasping at the back of her thigh to push her leg back, to make her more receptive and open to the growing base of her cock. “Trust me.”

She gave a few more messy thrusts, her whole body tensing as her breathing escalated and a drawn-out groan accompanied the harsh throb of her rock-hard length inside Mercy.

She forced herself forward and Mercy whimpered as the thick knot started to enter her.

It was painful, she knew it was, but all her body recognized was the pleasure of it as it slid into her inch after aching inch, as Zarya’s broad shoulders above her tensed and shook in anticipation of her own orgasm. Her inner muscles were clenched, ready, and all she needed was that final sensation to-

With an obscene noise, Zarya’s knot popped into her.

It twitched, once, and suddenly Mercy found herself tumbling over the edge, the relief of finally being knotted mixing with the sensation of reaching the peak she’d been denied for so long. Her cry was chocked and loud as the ball of arousal burst and waves of pleasure swept through her.

The uncontrolled trembling of her limbs was subdued as Zarya pushed down on her body and buried her face in the crook of her neck, opening her mouth to take her skin between her teeth in a harsh bite. It muffled the sound of her release as she jerked into her and came as her knot inflated to its full size, her cum filling Mercy in thick, hot ropes and getting sucked into her cervix as her walls tensed and released rhythmically in the throes of climax.

It didn’t stop. The force of her bite was overwhelming as Zarya kept pumping into her and Mercy’s eyes rolled into the back of her head when her own orgasm was immediately followed by another, her fingers scratching against the back of the Alpha’s head to keep her close, to encourage her into marking her for everyone to see.

Even as the rush of cum abated, the knot inside her kept throbbing and she knew it would continue to do so, continue to fill her with short, slow dribbles of semen, for as long as the two of them were tied.

And while she was satisfied for now, her limbs heavy as lead and her muscles quivering, the simmering arousal in her belly would not disappear until her heat had ended in a few days or until she was too sore and exhausted for her body to keep up.

Carefully, Zarya released the tight grip of her teeth on the skin of Mercy’s neck, her chest pumping as she breathed heavily. Even that simple movement caused another weak orgasm to shiver through Mercy as the knot inside her was jostled and gave another spurt of cum.

She was incredibly sensitive, more so than before, and everything almost felt like too much.

“Thank you for trusting me,” Zarya sighed, the tone of her voice and the happy glow in her eyes leaving no doubt about her sincerity. She brushed a sweat-matted strand of hair away from Mercy’s brow and smiled. “I am proud of you.”

The Alpha was large and warm and Mercy wrapped her arms tightly around her neck as the first tears began to fall. She didn’t know why she was crying or why the mere thought of even an inch of space between them made an invisible rope squeeze tight around her heart, but she couldn’t bring herself to stop even when Zarya lifted her gently upright and returned the embrace.

“I am here, Ангел. You are safe.”

The Alpha kept mumbling soothing words, rubbing circles over her upper back while Mercy sobbed and hiccupped into her shoulder. She hadn’t felt like this in years – like a child clinging to a stuffed toy, crying simply because she felt _too much_ , because she was happy and sad and vulnerable and too exhausted to hold anything back.

It took minutes for her heaving sobs to quiet down and even longer until she felt ready to lift her head and look Zarya in the eye.

 “I am sorry,” she said, wiping at the wetness on the other woman’s skin with trembling fingers. “I- I don’t know what came over me.”

A part of her wasn’t quite sure whether she was referring to the crying or what went down before it, but Zarya simply shook her head. “It is natural, yes?”

Mercy almost smiled. Most Omegas felt vulnerable in one way or another after being knotted during a heat, physically and emotionally, but that amount of sobbing was extreme and she suspected they both knew it.

“Do you,” For the first time since Mercy had known her, Zarya hesitated. She seemed to search for the right words, but met her eyes without fear once she had found them. “Were you crying because you regret mating with me?”

Mercy didn’t have to search herself for the answer. “No.”

She was sore and tired, like all her nerve endings and her heart lay bare and open for the world to see, but she didn’t regret it. Zarya was still here, still looked at her in the same way even now that her face was red and blotchy from crying, and Mercy felt at peace. As much as she couldn’t bring herself to say the words, not now and maybe not ever, she felt loved.

Zarya’s tense shoulders relaxed and she brushed her lips over both of Mercy’s eyelids, her drying cheeks and finally, her mouth.

“In that case,” she said with a light-hearted grin and rolled her hips, causing Mercy’s eyes to go wide and a gasp to hiss from between her teeth as her inner muscles eagerly grasped at the cock inside her, even as the rest of her protested. “Ready for Round 2?”

“No!”

Zarya laughed at her scandalized tone and the way her body betrayed her by inching closer anyway, and Mercy ineffectively shoved at her shoulder. “You are horrible.”

Still, she made no attempt to scold her further when the Alpha’s chuckle ebbed away and she slid both arms underneath her buttocks to lift her up and off the desk. Zarya looked around the room and frowned, apparently dissatisfied with what she was seeing, before carrying her across the room and carefully lowering herself to the floor until she could rest her back against the wall.

The Alpha hissed.

“Your back,” Mercy muttered apologetically as she settled more comfortably into her lap, ignoring the knot limiting her movements. “I scratched you.”

Zarya’s nod was oddly pleased. “I wear my battle scars proudly, Ангел.”

This time it was Mercy’s turn to laugh softly and she pressed her face into the other woman’s chest to muffle the sound. The bite mark on her neck twinged, but the thought of carrying a scar as proof of what they had done wasn’t unpleasant.

Silence descended as they sat there, Mercy’s body finally unwinding from the prolonged anticipation to allow her heartbeat to settle. The cooling sweat on her skin made her shiver where she wasn’t pressed against Zarya.

Without comment, a heavy garment appeared around her shoulders. Zarya’s jacket was soft and smelled exactly like her as it was wrapped around Mercy, building a comforting cocoon of body heat and Alpha scent.

“I’m going to fall asleep,” she protested weakly.

Zarya hummed and pulled her close, cradling her firmly to her chest. “Then sleep. I am here.”

With the steady rise and fall of Zarya’s breathing and her calming heartbeat against her ear, Mercy snuggled deeper into her and allowed her eyes to close. For once, she knew not even the nightmares would reach her – not as long as Zarya was there to chase them away.

**Author's Note:**

> Mercy has deep-seated issues and I love it.


End file.
